Thermal relay having movable heat transfer device



Aug. 31, 1965 J. GIGER 3,204,064

THERMAL RELAY HAVING MOVABLE HEAT TRANSFER DEVICE Filed Oct. 22, 1962 INVENTOR JAKOB GIGER MORGAN, FINNEGAN, DURHAM a PINE ATTORNEYS United States Patent 3,204,064 THERMAL RELAY HAVING MOVABLE HEAT TRANSFER DEVICE Jakob Giger, Zug, Switzerland, assignor to Landis & Gyr, A.G., Zug, Switzerland, a body corporate of Switzerland Filed Oct. 22, 1962, Ser. No. 231,905 Claims priority, application Switzerland, July 18, 1962,

6 Claims. Cl. 200-122 This invent-ion relates to relay devices and more particularly to thermal relay arrangements.

It is known to amplify small electric currents or volt ages to suchan extent that they can satisfactorily actuate higher rated relays having electric contacts adapted for many different purposes such as controlling the operation of servo-motors for actuating electrical controls.

A variety of constructions are known for such amplifiers including, for example, magnetic amplifiers and sensitive no-volt-age relays with large switching relays connected thereto.

Known amplifiers, however, not only have the disadvantage of high production costs but, owing to the larger number of structural parts, to their mechanical sensitivity and other factors, also have the disadvantage of being sensitive to considerable and varied disturbances.

It is one object of the invention to provide a relay which avoids these disadvantages.

This and other objects and advantages of the invention will be set forth in part hereinafter and in part will be obvious herefrom, or may be learned by practice with the invention, the same being realized and attained by means of the parts, constructions, arrangements, C0111 binations and improvements-pointed out in the appended claims.

The invention consists in the novel parts, constructions, arrangements, combinations and improvements herein shown and described.

Serving to illustrate an exemplary embodiment of the invention is the drawing comprising one figure, a perspective view of a bimetal relay according to the invention.

As may be seen in the figure, the illustrated relay has two bimetal contact devices and, arranged between them, a heat-conducting block which can be actuated by a transducer such as a rotor coil measuring mechanism.

The illustrated relay has two spaced, parallel bimetal laminations 41 and 42, one end portion of each being securely clamped in an electrical insulation block 43. In the vicinity of their other end portions the bimetal laminations 41 and 42 are mechanically connected by a web 44. The bimetal strips 41 and 42 are relatively arranged, for example, with their sides having the greater coetficient of expansion facing away from one another. Two ordinary contact springs 45 and 46 are mounted at a certain distance outside the bimetal laminations 41 and 42, one end portion of each being fixed in the block 43. Two opposed electric contact elements 47 and 48 are mounted on the bimetal lamination 41 and on the contact spring 45 respectively. The members 41, 45, 47 and 48 together form a first bimetal contact device having electric terminals 49 and 50. On the other bimetal lamination 42 and on the contact spring 46 there are also two opposed respective electric contact elements 51 and 52. The members 42, 46, 51 and 52 together form a second bimetal contact device, which is provided with electric terminals 53 and 54. By virtue of web 44, the two contact devices are differentially connected.

Midway between the bimetal strips 41 and 42 there is a shaft 55 connected to the rotor coil 56 of a rotor coil measuring mechanism 57. Mounted coaxially about the shaft 55 is a stationary electric heating winding 58 used as a heating means. The winding 58 is fixed on an insulating plate 59, which also carries the block 43, already mentioned, and has a hole for the passage of the shaft 55. Mounted on the shaft 55 and coaxial therewith is a housing 60 which is designed as a cylindrical casing and is made of material of good thermal conductance. The housing 60 encloses the heating winding 58. On the outside of the peripheral surface of the housing 60 there is a block 61 which is also made of material of good heat conductance and which can be reciprocated between the two bimetal strips 41 and 42 by rotating the shaft 55. The block has two oblique, level outer surfaces 61a and 6111, which can bear flatly on the one bimetal lamination 41 and on the other lamination 42 respectively when the block 61 is suitably pivoted.

The above-described bimetal relay is used and operated as follows:

The heating winding 58 is connected through its terminals 62 to a source of electric current (not shown) and thereby heated to a given temperature. The heat produced by the winding 58 is transferred by radiation and convection to the housing 60 and the block 61, so that the block acquires a temperature comparatively little below that of the heating winding 58.

The rotor coil 56 is connected, for example, to a bridge circuit (not shown), which is supplied from a current source (also not shown). If the bridge circuit is balanced, the rotor coil 56 assumes a position such that the block 61 is located cent-rally between the two bimetal strips 41 and 42. The heat given off by the housing 60 and by the block 61 acts uniformly on the two bimetal strips 41 and 42, so that the latter have the same temperature. Any bending of the bimetal strip 41 is opposed by identical bending of the other bimetal strip 42, and vice versa, since the strips are connected by the web 44. The contact elements 47 and 51 therefore remain in their rest position in spite of the heating of the bimetal strips 41 and 42.

If the bridge circuit is unbalanced, however, the rotor coil 56 is rotated in one or other direction, whereby the block 61 is moved towards and finally comes into contact with either the bimetal strip 41 of the bimetal strip 42. The bimetal strip which is closer to or in contact with the block 61 is heated more intensely than the other, thus producing deformation of the connected bimetal strips and movement of the contact elements, e.g., 47 and 51. If the sides of the bimetal strips 41 and 42 having the greater coefiicient of heat expansion face outwards, the contact elements 51 and 52 make contact when the block 61 is moved towards the bimetal strip 41. Conversely the contact elements 47 and 48 make contact when the block 61 is moved towards the bimetal strip 42. The block 61 accordingly enables one or the other of the bimetal strips to be thermally connected to the heating means 58.

The bimetal strips 41 and 42 can also be relatively arranged so that their sides having the greater coefficient of expansion are on the inside, i.e., facing one another. The reverse arrangement previously described is particularly favorable, however, since, when the block 61 is pivoted out of its central position, the more intensely heated bimetal strip bends towards the block 61 and is therefore heated to a still greater extent, thus accelerating the bending of the connected bimetal strips 41 and 42 and producing more rapid contact closing. Conversely, the opening of the contacts is also accelerated when the block 61 pivots back into its central position, since the bimetal strip which was previously heated more intensely simultaneously bends outwardly, i.e., away from the block,

so that cooling takes place more rapidly. The arrangement has the advantage that contact-making and contactopening is effected in a more positive manner.

The bimetal relay described enables other higher power circuits to be reliably controlled by small electric voltages or currents applied to the rotor coil 56, particularly with the aid of the robust contact elements 47, 48 and 51, 52 and the attendant, comparatively large, contact pressure. Moreover, only very small forces are required to pivot the rotor coil 56 and block 61, since the movable system has little mass moment of inertia and can be mounted almost without friction, for example by means of conical bearings. The contact pressure is produced by means of the heat energy acting on the bimetal strips 41 and 42.

The bimetal relay according to the invention has the advantage that with it strong contacts can be simply, cheaply and reliably operated with strong contact pressure from small measured values. It is distinctive in that the initial input need move only a small, light control element which is mountedalmost without friction and has a very low mass movement of inertia. The system thus requires only very small actuating forces. The necessary contact pressure is produced by the bimetal strips, so that the system according to the invention acts to a certain extent like a simple servo-system, where small force inputs, for example about 0.1 g., produce linear displacement of the heating or cooling lug which serves as a movably mounted control element, and where a contact force many times larger, for example about g., is nevertheless obtained with frictional contact-making.

A further advantage of the bimetal relay described is that, owing to the stationary arrangement of the heating means 58, no flexible wiring connections are needed for the heating winding. Further insulation of the coil 56 of the measuring mechanism from the heating winding 58 is easily effected.

The invention in its broader aspects is not limited to the specific mechanisms shown' and described but departures may be made therefrom within the, scope of the accompanying claims without departing from the principles of the invention and without sacrificing its chief advantages.

What is claimed is:

1. A thermal relay for providing an output indication in response to an applied electrical signal, comprising bimetallic contact means for providing said output indication; electromechanical means connectable for response to said applied electrical signal and operative to assume a position which is a function of said applied signal; heating means; and a thermally conductive control member positioned by said electromechanical means and mounted for movement into and out of engagement with said contact means, said control member being in heat conducting relationship with said heating means and selectively operable to transfer heat to said bimetallic contact means by direct contact therewith.

2. A thermal relay in accordance with claim 1 wherein said electromechanical means includes a moving electromagnetic coil disposed within a magnetic field, said coil being connected for response to said electrical signal.

3. A thermal relay in accordance with claim 1 wherein said heating means is a stationary electric heating coil and said control member includes a thermally conductive housing partially enclosing said coil.

4. A thermal relay for providing an output indication in response to an applied electrical signal, comprising a pair of contacts; a pair of spaced-apart bimetal members mechanically interconnected for synchronous movement between said contacts; electromechanical means connectable for response to said applied signal and operative to assume an angular position which is a function of said applied signal; heating means disposed between said bi metallic members; and a thermally conductive control member positioned by said electromechanic means and mounted for movement into and out of engagement with said bimetallic members, said control member being in heat conducting relationship with said heating means and selectively operable to transfer heat to said bimetallic members by direct contact therewith.

5. A thermal relay in accordance with claim 4 wherein said heating means is stationary and said control member is mounted to rotate about said stationary heating means.

6. A thermal relay in accordance with claim 5 wherein said control member includes at least two planar surfaces and is disposed so that one of said planar surfaces can engage one of said bimetallic members when said control member rotates in one direction and so that the other of said planar surfaces can engage the other of said bimetallic members when said control member rotates in the opposite direction.

References Cited by the Examiner UNITED STATES PATENTS 1,974,188 9/34 Martin 200-122 2,195,947 4/ 40 Uhlrig 200-122 2,225,975 12/ 40 Bruce 200-122 2,371,018 3/45 Asworth et al. 200-122 2,611,855 9/52 Turner 200-122 2,744,178 5/56 Eckberg 200-138 2,803,722 8/57 Kuhn 200-124 2,836,366 5/58 Eckberg.

2,969,917 1/61 Nason 200-122 3,064,103 11/62 Bierman et al 200-122 FOREIGN PATENTS 255,335 7/26 Great Britain.

References Cited by the Applicant FOREIGN PATENTS 409,605 12/ 42 Canada.

448,355 5/48 Canada.

485,713 8/52 Canada.

551,058 12/57 Canada. 1,109,484 1/57 France.

621,639 11/35 Germany.

730,547 1/ 43 Germany.

856,370 11/52 Germany. 1,077,446 3/60 Germany.

BERNARD A. GILHEANY, Primary Examiner. 

1. A THERMAL RELAY FOR PROVIDING AN OUTPUT INDICATION IN RESPONSE TO AN APPLIED ELECTRICAL SIGNAL, COMPRISING BIMETALLIC CONTACT MEANS FOR PROVIDING SAID OUTPUT INDICATION; ELECTROMECHANICAL MEANS CONNECTABLE FOR RESPONSE TO SAID APPLIED ELECTRICAL SIGNAL AND OPERATIVE TO ASSUME A POSITION WHICH IS A FUNCTION OF SAID APPLIED SIGNAL; HEATING MEANS; AND A THERMALLY CONDUCTIVE CONTROL MEMBER POSITIONED BY SAID ELECTROMECHANICAL MEANS AND MOUNTED FOR MOVEMENT INTO AND OUT OF ENGAGEMENT WITH SAID CONTACT MEANS, SAID CONTROL MEMBER BEING IN HEAT CONDUCTING RELATIONSHIP WITH SAID HEATING MEANS AND SELECTIVELY OPERABLE TO TRANSFER HEAT TO SAID BIMETALLIC CONTACT MEANS BY DIRECT CONTACT THEREWITH. 